JP6945732B2 - Natural gas liquefaction by high-pressure expansion process - Google Patents

Description

Cross-reference to related applications This application claims the priority benefit of US Provisional Application No. 62 / 565,725 filed on September 29, 2017 under the title of the invention "Natural gas liquefaction by high pressure expansion process". Incorporated herein by reference to the disclosure.
This application is in connection with US Provisional Application No. 62/565733, co-owned with it and filed on the same date under the title of the invention "Natural gas liquefaction by high pressure expansion process", by reference to its entire disclosure. Incorporated herein.

Background Disclosure This disclosure generally relates to the production of liquefied natural gas (LNG). More specifically, the present disclosure relates to LNG production at high pressure.

Description of Related Techniques This section is intended to introduce various aspects of the art that may be relevant to this disclosure. This discussion is intended to provide a framework for facilitating a better understanding of certain aspects of this disclosure. Therefore, it should be understood that this section should be judged from this point of view and not necessarily the approval of the prior art.
Natural gas has become widely used in recent years due to its clean flammability and convenience. Many natural gas sources are located in remote areas far from any commercial market for gas. Pipelines may also be used to transport the natural gas produced to the commercial market. When pipeline transport is not feasible, the natural gas produced is often processed into liquefied natural gas (LNG) for transport to the market.

One of the most important considerations in designing an LNG plant is the process of converting the natural gas supply to LNG. Currently, the most common liquefaction process uses some form of cooling system. Although many cooling cycles are used to liquefy natural gas, the three most commonly used types today in LNG plants are (1) multiple in continuously arranged heat exchangers. A "cascade cycle" that uses a single-component refrigerant to lower the gas temperature to the liquefaction temperature, (2) a "multi-component cooling cycle" that uses a multi-component refrigerant in a specially designed exchanger, and (3) a gas supply. It is an "expansion cycle" that expands from gas pressure to low pressure and the temperature drops accordingly. Most natural gas liquefaction cycles use variants or combinations of these three basic types.

In a multi-component refrigerant cycle, the refrigerant used in the liquefaction process may include a mixture of components such as methane, ethane, propane, butane, and nitrogen. In the "cascade cycle", the refrigerant may be a pure substance such as propane, ethylene, or nitrogen. A considerable volume of these refrigerants is required with close control of the composition. In addition, the refrigerant may have to be imported and stored, especially for LNG production in remote areas, which imposes logistics requirements. Alternatively, some of the components of the refrigerant may be prepared by a distillation process typically integrated with the liquefaction process.

The use of gas expanders to allow cooling of the feed gas, thereby eliminating or alleviating logistics problems in the handling of refrigerants, may be found to have advantages over refrigerant-based cooling. The inflator system operates on the principle that the refrigerant gas can be expanded through an expansion turbine, thereby performing work and lowering the temperature of the gas. The cold gas is then heat exchanged with the supply gas to provide the required cooling. The forces obtained from the cooling expansion in the gas expander can be used to supply a portion of the main compressive force used in the cooling cycle. A typical inflator cycle for producing LNG typically operates at a supply gas pressure of less than about 6,895 kPa (1,000 psia). Supplemental cooling is typically required to completely liquefy the supply gas, which can be provided by additional cooling systems such as secondary cooling and / or subcooling loops. For example, US Pat. No. 6,412,302 and US Pat. No. 5,916,260 propose an inflator cycle that uses nitrogen as the refrigerant in the subcooling loop.

However, all previously proposed inflator cycles are thermodynamically less efficient than current natural gas liquefaction cycles based on refrigerant systems. Therefore, the expander cycle has so far not provided any installation cost advantage, and the liquefaction cycle requiring a refrigerant is still the preferred option for natural gas liquefaction.
Gas expanders typically use an external refrigerant, for example, in a closed cycle to feed the gas, as the inflator cycle results in high recirculation gas flow velocity and high inefficiency for the primary cooling (warm) stage. It is used to cool it further after precooling it to a temperature well below 20 ° C. Therefore, a common factor in most proposed inflator cycles is the need for a second external cooling cycle to precool the gas before it enters the inflator. Such a combined external cooling cycle and inflator cycle is sometimes referred to as a "hybrid cycle". Such refrigerant-based precooling eliminates the main cause of inefficiency in using the inflator, but greatly reduces the benefit of the inflator cycle, i.e. the elimination of external refrigerant.

U.S. Patent Application US / 0217701 introduces the concept of using high pressure in the primary cooling loop to eliminate the need for external refrigerants and improve efficiency at least comparable to the refrigerant-based cycles currently in use. bottom. The High Pressure Inflator Process (HPXP) disclosed in US Patent Application US / 0217701 is an inflator cycle that uses a high pressure inflator in a manner that distinguishes it from other inflator cycles. A portion of the supply gas stream can be extracted and used as a refrigerant in either an open-loop or closed-loop cooling cycle to cool the supply gas stream below its critical temperature. Alternatively, a portion of the LNG boil-off gas can be extracted and used as a refrigerant in a closed-loop cooling cycle to cool the supply gas stream below its critical temperature. This cooling cycle is called the primary cooling loop. The primary cooling loop is followed by a sub-cooling loop that acts to further cool the supply gas. Within the primary cooling loop, the refrigerant is compressed to a pressure above 10342 kPa (1,500 psia), more preferably to a pressure of approximately 20664 kPa (3,000 psia). The refrigerant is then cooled in contact with the ambient cooling medium (air or water) and then expands almost equitropically to provide the cold refrigerant needed to liquefy the supply gas.

FIG. 1 shows an example of a known HPXP liquefaction process 100, similar to one or more processes disclosed in US 2009/0217701. In FIG. 1, an inflator loop 102 (ie, an inflator cycle) and a subcooling loop 104 are used. The supply gas flow 106 is less than about 8274 kPa (1,200 psia), or less than about 7584 kPa (1,100 psia), or less than about 6,895 kPa (1,000 psia), or less than about 6205 kPa (900 psia), or less than about 5516 kPa (800 psia), or Enter the HPXP liquefaction process at a pressure of less than about 4826 kPa (700 psia) or less than about 4137 kPa (600 psia). Typically the pressure of the supply gas stream 106 is about 5516 kPa (800 psia). The feed gas stream 106 generally comprises natural gas that has been treated with technically well-known processes and equipment to remove contaminants.

In the inflator loop 102, the compression unit 108 compresses the refrigerant flow 109 (which can be a treated gas flow) to a pressure of about 10342 kPa (1,500 psia) or higher, thus providing the compressed refrigerant flow 110. Instead, the refrigerant flow 109 is about 11032 kPa (1,600 psia) or more, or about 11721 kPa (1,700 psia) or more, or about 12411 kPa (1,800 psia) or more, or about 13100 kPa (1,900 psia) or more, or about 13790 kPa (2,000 psia) or more. , Or compression to a pressure of about 17237 kPa (2,500 psia) or higher, or about 20684 kPa (3,000 psia) or higher, thus providing a compressed refrigerant flow 110. After leaving the compression unit 108, the compressed refrigerant stream 110 is sent to the cooler 112, where it is cooled by indirect heat exchange with a suitable cooling fluid to provide the compressed and cooled refrigerant stream 114. The cooler 112 may be of a type that provides water or air as the cooling fluid, but any type of cooler can be used. The temperature of the compressed and cooled refrigerant stream 114 depends on the ambient conditions used and the cooling medium, typically from about 1.67 ° C (35 ° F) to about 40.56 ° C (105 ° F). The compressed and cooled refrigerant stream 114 is then sent to the expander 116 where it expands and continues to cool to form the expanded refrigerant stream 118. The inflator 116 is a work inflator, such as a gas inflator, that produces workpieces that can be extracted and used for compression. The expanded refrigerant flow 118 is sent to the first heat exchanger 120, providing at least a portion of the cooling capacity for the first heat exchanger 120. As soon as it exits the first heat exchanger 120, the expanded refrigerant flow 118 is supplied to the compression unit 122 for pressurization to form the refrigerant flow 109.

The supply gas stream 106 flows through the first heat exchanger 120 and is at least partially cooled by indirect heat exchange with the expanded refrigerant stream 118. After exiting the first heat exchanger 120, the supply gas stream 106 is sent to the second heat exchanger 124. The main function of the second heat exchanger 124 is to sub-cool the supply gas flow. Therefore, in the second heat exchanger 124, the supply gas flow 106 is sub-cooled by the sub-cooling loop 104 (described later) to generate the sub-cooling flow 126. The sub-cooling stream 126 then expands to a lower pressure in the inflator 128 to form a liquid fraction and a residual vapor fraction. The expander 128 may be any decompression device, and examples thereof include, but are not limited to, a valve, a control valve, a Joule-Thomson valve, a Venturi device, a liquid expander, and a hydraulic turbine. The now lower pressure, partially liquefied sub-cooling stream 126 is sent to the surge tank 130, where the liquefied fraction 132 is removed from the process as an LNG stream 134 with a temperature corresponding to the boiling pressure. The residual steam fraction (flash steam) stream 136 is available as a fuel to power the unit for compression.

Within the sub-cooling loop 104, the expanded sub-cooling refrigerant flow 138 (preferably containing nitrogen) is discharged from the expander 140 and drawn through the second and first heat exchangers 124, 120. The expanded sub-cooling refrigerant flow 138 is then sent to the compression unit 142 to be recompressed to a higher pressure and warmed. After leaving the compression unit 142, the recompressed subcooling refrigerant stream 144 is cooled in the cooler 146. The cooler 146 may be of the same type as the cooler 112, but any type of cooler may be used. After cooling, the recompressed sub-cooling refrigerant flow is sent to the first heat exchanger 120 and further cooled by indirect heat exchange with the expanded refrigerant flow 118 and the expanded sub-cooling refrigerant flow 138. After exiting the first heat exchanger 120, the recompressed and cooled sub-cooling refrigerant stream expands through the expander 140 to provide a cooling stream, which is then the second heat exchange. It passes through the vessel 124 and subcools the portion of the supply gas stream that will eventually expand to produce LNG.

U.S. Pat. No. Disclosure of improvements to HP XP performance through. The HPXP embodiment described in the above patent application works to the same extent as an alternative mixed external refrigerant LNG generation process such as a single mixed refrigerant process. However, there remains a need to further improve not only the efficiency of HPXP, but also the overall train capability. There remains a need to improve the efficiency of HPXP, especially when the supply gas pressure is less than 8274 kPa (1,200 psia).

U.S. Patent Application 2010/0186445 disclosed the incorporation of feedstock compression up to 31026 kPa (4,500 psia) into HPXP. Compressing the feed gas before liquefying it in the HPXP primary cooling loop has the advantage of increasing overall process efficiency. Due to the given production rate, this also has the advantage of significantly reducing the required flow rate of the refrigerant in the primary cooling loop, which allows the use of small equipment, which is particularly attractive for floating LNG applications. .. In addition, feedstock compression provides a means of increasing the LNG production rate of HPXP trains by more than 30% due to the fixed amount of force towards the primary and sub-cooling loops. This adaptability of the production rate is again particularly attractive for floating LNG applications, which are more limited than ground-based applications in matching the refrigerant loop driver selection with the desired production rate. Although liquefying the feed gas at high pressure has advantages, choosing a cryogenic heat exchanger suitable for the primary cooling and sub-cooling loops due to the liquefaction pressure above 10342 kPa (1,500 psia) is very costly and heavy. , It turned out that it is limited to the options with reduced fluid processing capacity. For example, the use of printed circuit heat exchangers that can operate at pressures above 31026 kPa (4,500 psia) will result in more widely procured brazed aluminum heat exchanger types with proven operating pressures below 10342 kPa (1,500 psia). It was found that the project cost was significantly higher than that. This significant increase in cost could limit the actual application of feedstock compression to 10342 kPa (1,500 psia). Therefore, there remains a need to further improve HPXP without the need for feedstock compression or feedstock compression above 10342 kPa (1,500 psia). In addition, there remains an additional need to enable the use of significant feedstock compression in HPXP without the need for costly main cryogenic heat exchangers such as printed circuit heat exchangers.

Summary The present disclosure is a method of liquefying a methane-rich feed gas stream using a system with first and second heat exchanger zones, the following steps: feed gas stream at a pressure of less than 8274 kPa (1,200 psia). To prepare a compressed refrigerant stream with a pressure of 10342 kPa (1,500 psia) or higher; this compressed refrigerant stream was cooled, compressed and cooled by indirect heat exchange with ambient temperature air or water. Generating a stream of refrigerant; this compressed and cooled stream of refrigerant is sent to a second heat exchanger zone to further cool the compressed and cooled stream of refrigerant below ambient temperature, compress and further. To generate a cooled refrigerant flow; to expand this compressed and further cooled refrigerant flow in at least one workpiece-generating inflator to generate an expanded cooling refrigerant flow; this expanded cooling refrigerant. Passing the flow through the first heat exchanger zone to form a first hot refrigerant flow (this first hot refrigerant flow is at least 2.8 ° C above the maximum fluid temperature in the first heat exchanger zone (). 5 ° F) has a cold temperature); the supply gas flow is passed through the first heat exchanger zone to cool at least part of the supply gas flow by indirect heat exchange with the expanded cooling refrigerant flow, thereby liquefying. Forming a gas stream; sending at least a portion of the first hot refrigerant stream to the second heat exchanger zone to cool the compressed and cooled refrigerant stream by indirect heat exchange, thereby cooling the second. Provided are methods comprising forming a hot refrigerant stream; and compressing a second warm refrigerant stream to produce a compressed refrigerant stream.

The present disclosure also provides a system for liquefying a methane-rich supply gas stream, which also has first and second heat exchanger zones. A supply gas stream is prepared at a pressure of less than 8274 kPa (1,200 psia). The compressed refrigerant flow has a pressure of 10342 kPa (1,500 psia) or higher. The cooler is configured to cool the compressed refrigerant stream by indirect heat exchange with ambient temperature air or water to produce a compressed and cooled refrigerant stream. At least one heat exchanger is provided in the second heat exchanger zone, and a compressed and cooled refrigerant stream is sent to this at least one heat exchanger in the second heat exchanger zone. The compressed and cooled refrigerant stream is further cooled below ambient temperature, thereby producing a compressed and further cooled refrigerant stream. At least one work-generating expander is placed to expand this compressed and further cooled refrigerant stream, thereby generating an expanded cooling refrigerant stream. At least one heat exchanger is provided in the first heat exchanger zone. The expanded cooling refrigerant flow passes through at least one heat exchanger in the first heat exchanger zone to form the first warm refrigerant flow. This first hot refrigerant stream has a temperature at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone. The supply gas flow passes through the first heat exchanger zone and indirect heat exchange with the expanded cooling refrigerant flow cools at least a portion of the supply gas flow, thereby forming a liquefied gas flow. At least a portion of the first hot refrigerant flow is sent to the second heat exchanger zone to cool the compressed and cooled refrigerant flow by indirect heat exchange, thereby forming a second warm refrigerant flow. do. The compressor is configured to compress the second warm refrigerant stream to produce a compressed refrigerant stream.

The present disclosure is a method of liquefying a methane-rich feed gas stream, in which the following steps: prepare the feed gas stream at a pressure of less than 8274 kPa (1,200 psia); the feed gas stream at a pressure of at least 10342 kPa (1,500 psia). Compress to form a compressed gas stream; cool the compressed gas stream by indirect heat exchange with ambient temperature air or water to form a cooled compressed gas stream; this cooled compressed gas stream Inflate to a pressure below 13790 kPa (2,000 psia) and below the compressed pressure in at least one workpiece-forming inflator, thereby forming a cooling gas flow; a pressure above 10342 kPa (1,500 psia). To prepare a compressed refrigerant stream with; to cool this compressed refrigerant stream by indirect heat exchange with ambient temperature air or water to form a compressed and cooled refrigerant stream; this compressed and cooled Sending a stream of refrigerant to a second heat exchanger zone to further cool the compressed and cooled refrigerant stream below ambient temperature to produce a compressed and further cooled refrigerant stream; this compressed and cooled refrigerant stream. Further, the cooled refrigerant flow is expanded in at least one work-generating expander to generate an expanded cooling refrigerant flow; this expanded cooling refrigerant flow is passed through the first heat exchanger zone. Forming a hot refrigerant flow of 1 (thus the first warm refrigerant flow has a temperature at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone); this cooling gas Passing the flow through the first heat exchanger zone to cool at least part of the cooling gas flow by indirect heat exchange with the expanded cooling refrigerant, thereby forming a liquefied gas flow; the first warm refrigerant flow. Sending to a second heat exchanger zone to cool the compressed and cooled refrigerant stream by indirect heat exchange, thereby forming a second warm refrigerant stream; and compressing the second warm refrigerant stream. Also provided are methods that include forming a compressed refrigerant stream.

The present disclosure also provides a system for liquefying a feed gas stream rich in methane and having a pressure of less than 8274 kPa (1,200 psia). This system is a compressor for compressing the supply gas flow to a pressure of at least 10342 kPa (1,500 psia) to form a compressed gas flow; cooling the compressed gas flow by indirect heat exchange with ambient temperature air or water. A cooler for forming a cooled compressed gas stream; the cooled compressed gas stream is expanded to a pressure of less than 13790 kPa (2,000 psia) and below the compressed pressure, thereby causing the cooling gas stream to expand. At least one workpiece-forming inflator to form; compressed refrigerant flow with a pressure of 10342 kPa (1,500 psia) or higher; compressed cooling by cooling the compressed refrigerant flow by indirect heat exchange with ambient temperature air or water. Refrigerant cooler for generating refrigerant flow; heat exchanger zone where compressed cooling refrigerant flow is sent through it to further cool below ambient temperature to produce compressed and further cooled refrigerant flow. An additional work-generating inflator for expanding the compressed and further cooled refrigerant flow to generate the expanded cooling refrigerant flow; passing the expanded cooling refrigerant flow through it, thereby the first temperature. An additional heat exchanger zone forming the refrigerant flow (thus the warm refrigerant flow has a temperature at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone; the cooling gas flow At least part of the cooling gas stream is cooled by indirect heat exchange with the expanded cooling refrigerant through an additional heat exchanger zone, thereby forming a liquefied gas stream; the first warm refrigerant stream is heat. It is sent to the exchanger zone to cool the compressed cooling refrigerant flow by indirect heat exchange, thereby forming a second warm refrigerant flow); and compressing the second warm refrigerant flow to create a compressed refrigerant flow. Includes additional compressor to generate.

The above has broadly outlined the features of the present disclosure so that the following detailed description can be better understood. Further features are also described herein.
These and other features, aspects and advantages of the present disclosure will become apparent from the description below, the appended claims and the accompanying drawings briefly described below.

It is a schematic diagram of the system for LNG generation according to a known principle. It is a schematic diagram of the system for LNG generation according to the disclosure aspect. It is a schematic diagram of the system for LNG generation according to the disclosure aspect. It is a schematic diagram of the system for LNG generation according to the disclosure aspect. It is a schematic diagram of the system for LNG generation according to the disclosure aspect. It is a schematic diagram of the system for LNG generation according to the disclosure aspect. It is a schematic diagram of the system for LNG generation according to the disclosure aspect. It is a schematic diagram of the system for LNG generation according to the disclosure aspect. It is a schematic diagram of the system for LNG generation according to the disclosure aspect. It is a flow chart of the method according to the aspect of this disclosure. It is a flow chart of the method according to the aspect of this disclosure. It is a flow chart of the method according to the aspect of this disclosure.

It should be noted that the figures are merely examples and are not intended to limit the scope of this disclosure. Moreover, the figures are generally drawn for convenience and clarity in describing the various aspects of the present disclosure, rather than the exact ratio.

Detailed explanation In order to promote understanding of the principles of the present disclosure, the features shown in the drawings will be referred to and the features will be explained using specific terms. Nonetheless, there is a consensus that the scope of this disclosure is intended without limitation. Any modification or further modification of the principles of disclosure described herein, as well as any further application, is intended to be generally noticed by those skilled in the art to which this disclosure relates. For clarity, features not relevant to this disclosure may not be shown in the drawings.

For reference, the specific terms used in this application and their meanings are first described in this context. Unless the term used herein is defined below, the broadest definition given to such term by one of ordinary skill in the art as in at least one publication or issued patent should be given. Moreover, all equivalents, synonyms, new developments, and terms or techniques that serve the same or similar purpose are considered to be within the scope of this claim and are not limited by the usage of the terms given below.

As a matter of course to those skilled in the art, the same feature or component may be referred to by a person under a different name. This document is not intended to distinguish between components or features that differ only in name. The figure is not always the exact ratio. Certain features and components herein may be exaggerated or shown in schematic form, and ordinary elements may not be shown for clarity and convenience. When referring to the drawings described herein, the same reference number may be referred to in a plurality of figures for simplicity. In the description and claims below, the terms "including" and "comprising" are used in an unlimited manner and should therefore be construed to mean "including, but not limited to". be.
The articles "the", "a" and "an" do not necessarily mean only one, and may be comprehensive and unlimited to include a plurality of such elements.

As used herein, the terms "approximately,""about,""substantially," and similar terms are commonly and accepted by those skilled in the art to which the subject matter of this disclosure is relevant. It is intended to have a broad meaning according to the usage. Those skilled in the art reviewing this disclosure understand that the description and assertion of certain features is intended to allow these terms without limiting the scope of these features to the exact numerical range provided. Should. Therefore, these terms should be construed as indicating that any non-substantial or insignificant amendments or changes to the described subject matter are considered to be within the scope of this disclosure. The term "near" is intended to mean within 2%, or within 5%, or within 10% of a number or quantity.
As used herein, the term "compression unit" means any one type of compression equipment or a combination of similar or different types of compression equipment, technically for compressing a substance or mixture of substances. Well-known auxiliary equipment may be included. A "compression unit" may utilize one or more compression steps. Examples of compressors include, but are not limited to, positive displacement type compressors such as reciprocating compressors and rotary compressors, and dynamic compressors such as centrifugal compressors and axial flow compressors.

As used herein, "typical" is used only to mean "useful as an example, example, or illustration." Any embodiment or embodiment described herein as "typical" should not be construed as preferred or advantageous over other embodiments.
The term "gas" is used interchangeably with "vapor" and is defined as a substance or mixture of substances in a gaseous state that distinguishes it from a liquid or solid state. Similarly, the term "liquid" means a substance or mixture of substances in a liquid state that distinguishes it from a gas or solid state.
As used herein, "heat exchange region" means any one of the technically well-known types of equipment or a combination of similar or different types of equipment to facilitate heat transfer. Thus, the "heat exchange region" may include a region that may be included within an integral device or that may be included within a plurality of device components. On the contrary, a plurality of heat exchange regions may be included in one device.

"Hydrocarbons" mainly include hydrogen and carbon elements, but may be present in small amounts of nitrogen, sulfur, oxygen, metals or any number of other elements. As used herein, hydrocarbons generally refer to components found in natural gas, oils, or chemical processing facilities.
As used herein, "loop" and "cycle" are used interchangeably.
As used herein, "natural gas" means a gaseous source suitable for the production of LNG, which source is methane-rich gas containing methane (C1) as the main component. Natural gas may include gas obtained from crude oil wells (accompanying gas) or gas obtained from gas wells (non-associated gas).

The present disclosure describes processes / methods and systems for liquefying natural gas streams and other methane-rich gas streams to produce liquefied natural gas (LNG) and / or other liquefied methane-rich gases. In one or more aspects of the present disclosure, the primary cooling loop is divided into two heat exchanger zones. In the first heat exchanger zone, the supply gas is liquefied using the primary cooling loop refrigerant. In the second heat exchanger zone, the high pressure primary cooling loop refrigerant is cooled with all or part of the primary cooling loop refrigerant and then expanded. The first heat exchanger zone is physically separated from the second heat exchanger zone. Further, the heat exchanger type in the first heat exchanger zone is different from the heat exchanger type in the second heat exchanger zone. One advantage of having two separate heat exchanger zones is that the types of heat exchangers in the two zones can differ from each other. As a non-limiting example, the type of heat exchanger (s) used in the first heat exchanger zone may include a braided aluminum heat exchanger and the heat exchangers (s) used in the second heat exchanger zone. (Yes) type may include a printed circuit type heat exchanger. It is in the first heat exchanger that more than 90% of the heat transfer required for liquefaction of the supply gas occurs. Using a low-cost brazed aluminum heat exchanger here will reduce project costs. A very expensive printed circuit heat exchanger can be used in the second heat exchanger zone as it can operate at the required 20664 kPa (3,000 psia) pressure of high pressure refrigerant. The use of printed circuit heat exchangers in the second heat exchanger zone does not significantly affect the overall project cost as it is a relatively small heat exchanger. This is because the heat transfer load in the second heat exchanger zone is considerably smaller than the heat transfer load in the first heat exchanger zone. Both heat exchanger zones may include multiple heat exchangers.

In one aspect, the method of liquefying the gas stream, especially the methane-rich gas stream, is as follows: (a) Prepare the supply gas stream at a pressure less than 8274 kPa (1,200 psia); (b) 10342 kPa (1,500 psia) or more. To prepare a compressed refrigerant having a pressure of; (c) cool this compressed refrigerant by indirect heat exchange with ambient temperature air or water to produce a compressed and cooled refrigerant; (d) this. Sending the compressed and cooled refrigerant to a second heat exchanger zone to further cool the compressed and cooled refrigerant below ambient temperature to produce a compressed and further cooled refrigerant; ( e) Expand this compressed and further cooled refrigerant in at least one workpiece-forming expander to produce the expanded cooling refrigerant; (f) use this expanded cooling refrigerant in the first heat exchanger. Forming a first hot refrigerant through the zone, thereby having a temperature at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone. And the heat exchanger type in the first heat exchanger zone is different from the heat exchanger type in the second heat exchanger zone); (g) The gas stream passed through the first heat exchanger zone and expanded. Cooling at least part of the gas stream by indirect heat exchange with the cooling refrigerant, thereby forming a liquefied gas stream; (h) Passing at least part of the first warm refrigerant through the second heat exchanger zone. By indirect heat exchange, the compressed and cooled refrigerant is cooled, thereby forming a second warm refrigerant; and (i) compressing this second warm refrigerant to produce a compressed refrigerant. include.

In another embodiment, the method of liquefying the gas stream is as follows: (a) prepare the feed gas stream at a pressure less than 8274 kPa (1,200 psia); (b) make this gas stream a pressure of at least 10342 kPa (1,500 psia). Compressing to form a compressed gas stream; (c) Cooling this compressed gas stream by indirect heat exchange with ambient temperature air or water to form a compressed and cooled gas stream; ( d) This compressed and cooled gas stream is expanded in at least one workpiece-forming inflator to a pressure of less than 13790 kPa (2,000 psia) and below the compressed pressure, thereby forming a cooling gas stream. To do; (e) Prepare a compressed refrigerant with a pressure of 10342 kPa (1,500 psia) or higher; (f) Cool the compressed refrigerant by indirect heat exchange with ambient temperature air or water to compress and cool. Producing compressed refrigerant; (g) this compressed and cooled refrigerant is sent to a second heat exchanger zone to further cool the compressed and cooled refrigerant below ambient temperature and compress. To produce a further cooled refrigerant; (h) to expand this compressed and further cooled refrigerant in at least one workpiece-forming inflator, thereby producing an expanded cooling refrigerant; (i). Passing this expanded cooling refrigerant through the first heat exchanger zone to form the first hot refrigerant (so that the first hot refrigerant is at least 2.8 above the maximum fluid temperature in the first heat exchanger zone. ℃ (5 ° F) cold temperature, and the heat exchanger type in the first heat exchanger zone is different from the heat exchanger type in the second heat exchanger zone); (j) Cooling gas flow Through the first heat exchanger zone, at least a part of the cooling gas flow is cooled by indirect heat exchange with the expanded cooling refrigerant, thereby forming a liquefied gas flow; (k) the first warm refrigerant. To the second heat exchanger zone to cool the compressed cooling refrigerant by indirect heat exchange, thereby forming a second warm refrigerant; and (l) compress this second hot refrigerant. Includes the production of compressed refrigerant.

In another embodiment, the method of liquefying the gas stream is as follows: (a) Prepare the supply gas stream at a pressure less than 8274 kPa (1,200 psia); (b) Prepare the refrigerant stream at almost the same pressure as this gas stream. To do; (c) mix the gas stream with the refrigerant stream to form a second gas stream; (d) compress this second gas stream to a pressure of at least 10342 kPa (1,500 psia) and compress it. Forming a second gas stream; (e) This compressed second gas stream is cooled by indirect heat exchange with ambient temperature air or water to create a compressed and cooled second gas. Forming a stream; (f) Send this compressed and cooled second gas stream to the second heat exchanger zone to further bring the compressed and cooled second gas stream below ambient temperature. Cooling to produce a compressed and further cooled second gas stream; (g) This compressed and further cooled second gas stream is 13790 kPa (2,000) in at least one workpiece-forming inflator. psia) The expansion of the second gas stream to a pressure below the compressed pressure, thereby expanding and forming a cooled second gas stream; (h) this expanded and cooled second gas stream. Dividing the second gas flow into a first expanding refrigerant and a cooling gas flow; (i) expanding the first expanding refrigerant in at least one workpiece-forming inflator, thereby producing a second expanding refrigerant. (J) Passing this second expanding refrigerant through the first heat exchanger zone to form the first hot refrigerant (so that the first hot refrigerant is the highest in the first heat exchanger zone. It has a temperature at least 2.8 ° C (5 ° F) cooler than the fluid temperature, and the heat exchanger type in the first heat exchanger zone is different from the heat exchanger type in the second heat exchanger zone); (k ) Passing the cooling gas stream through the first heat exchanger zone to cool at least part of the cooling gas stream by indirect heat exchange with the second expanding refrigerant, thereby forming a liquefied gas stream; (l) Sending the first warm refrigerant to the second heat exchanger zone and cooling the compressed and cooled second gas stream by indirect heat exchange to form the second warm refrigerant; and (m). ) Includes compressing this second warm refrigerant to generate a refrigerant flow.

The embodiment of the present disclosure is to compress the gas stream to a pressure of 11032 kPa (1,600 psia) or less before sending the gas stream to the first heat exchanger zone, and then combine this compressed gas stream with air or water at ambient temperature. It may include an additional step of cooling by indirect heat exchange. Aspects of the present disclosure may include an additional step of cooling the gas stream to a temperature below ambient temperature by indirect heat exchange within an external cooling unit before sending the gas stream to the first heat exchanger zone. Aspects of the present disclosure are that the compressed and cooled refrigerant is cooled to a temperature below ambient temperature by indirect heat exchange with an external cooling unit before the compressed and cooled refrigerant is sent to the second heat exchanger zone. It may also include additional steps to be performed. These additional steps described can be used alone or in combination with each other.

Aspects of the present disclosure have several advantages over known liquefaction processes that require compression of feedstock to greatly improve the efficiency of HPXP. In contrast, the efficiency of the disclosed embodiment is 16% higher than that for equivalent structures according to known liquefaction processes. Aspects of the present disclosure have the added benefit of enabling significant feedstock compression (> 10342 kPa (1,500 psia)) without the need to use a high cost major cryogenic heat exchanger in the first heat exchanger zone. Can have. Feed material compression according to the disclosure method may provide a means of increasing LNG production in HPXP trains by more than 25% due to a fixed amount of force going to the primary cooling and subcooling loops. Aspects of the present disclosure may also have the advantage of combining some of the primary cooling loops to reduce the supply gas compression service and the number of devices. The embodiment enables a compact structure suitable for high efficiency and small-scale LNG applications.

FIG. 2 is a schematic diagram showing a liquefaction system 200 according to the disclosure mode. The liquefaction system 200 includes a primary cooling loop 202, sometimes referred to as an inflator loop. The liquefaction system also includes a sub-cooling loop 204, which is a closed cooling loop filled with nitrogen, preferably as a sub-cooling refrigerant. In the primary cooling loop 202, the expanded cooling refrigerant flow 205 is sent to the first heat exchanger zone 201 and exchanges heat with the supply gas flow 206 to form the first warm refrigerant flow 208. A portion of this first hot refrigerant 208 is sent to the second heat exchanger zone 210 to exchange heat with the compressed and cooled refrigerant stream 212 in one or more heat exchangers 210a. The compressed and cooled refrigerant stream is further cooled to form a second warm refrigerant stream 209 and a compressed and further cooled refrigerant stream 213. The one or more heat exchangers 210a may be a printed circuit type heat exchanger type, a shell and tube heat exchanger type, or a combination thereof. The heat exchanger type in the second heat exchanger zone has a design pressure of more than 10342 kPa (1,500 psia), more preferably a design pressure of more than 13790 kPa (2,000 psia), even more preferably a design pressure of more than 20664 kPa (3,000 psia). Can have design pressure.

The portion of the first hot refrigerant flow 208 sent to the second heat exchanger zone 210 is at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone 201, more preferably. , At least 5.6 ° C (10 ° F) cold, more preferably at least 8.3 ° C (15 ° F) cold. The portion of the first warm refrigerant flow 208 (indicated by reference number 208a) that may remain in the first heat exchanger zone further heat exchanges with the supply gas stream to form a third warm refrigerant flow 214. The second hot refrigerant flow 209 from the second heat exchanger zone 210 may be combined with the third hot refrigerant flow 214 from the first heat exchanger zone 201 to generate a fourth hot refrigerant flow 216. .. This fourth hot refrigerant flow is compressed to a pressure above 10342 kPa (1,500 psia), more preferably about 20664 kPa (3,000 psia) in one or more compression units 218, 220 to form a compressed refrigerant flow 222. do. The compressed refrigerant stream 222 is then cooled in contact with the ambient cooling medium (air or water) in the cooler 224 to produce a compressed and cooled refrigerant stream 212. The cooler 224 may be similar to the cooler 112 described above. The compressed and further cooled refrigerant flow 213 expands almost equientropically in the expander 226 to produce an expanded cooling refrigerant flow 205. The inflator 226 may be a work inflator, such as a gas inflator, that produces a work that can be extracted and used for compression.

The first heat exchanger zone 201 may include a plurality of heat exchangers, and in the embodiment shown in FIG. 2, the first heat exchanger zone includes the first and second main heat exchangers 232, 234. The sub-cooling heat exchanger 236 includes and exchanges heat with the expanded cooling refrigerant 205. These heat exchangers may be brazed aluminum heat exchanger type, plate fin heat exchanger type, spiral heat exchanger type, or a combination thereof. Within the sub-cooling loop 204, the expanded sub-cooling refrigerant flow 238 (preferably containing nitrogen) is discharged from the expander 240 to the sub-cooling heat exchangers 236, second and first main heat exchangers 234, 232. Pulled out through. The expanded sub-cooling refrigerant flow 238 is then sent to the compression unit 242, where it is recompressed to a higher pressure and warmed. After leaving the compression unit 242, the recompressed subcooling refrigerant flow 244 is cooled in the cooler 246. The cooler 246 may be of the same type as the cooler 224, but any type of cooler may be used. After cooling, the recompressed sub-cooling refrigerant flow passes through the first and second main heat exchangers 232, 234, in which the warm refrigerant flow 208 and part or all of the expanded sub-cooling refrigerant flow 238. Further cooled by indirect heat exchange. After exiting the first heat exchange region 201, the recompressed and cooled subcooling refrigerant flow expands through the expander 240 to provide the expanded subcooling refrigerant flow 238. It is recirculated through the first heat exchanger zone as described herein. Thus, the supply gas stream 206 is cooled, liquefied and subcooled in the first heat exchanger zone 201 to produce a subcooled gas stream 248. The sub-cooling gas stream 248 then expands within the inflator 250 to a lower pressure to form a liquefied fraction and a residual vapor fraction. The expander 250 may be any decompression device, and examples thereof include, but are not limited to, a valve, a control valve, a Joule-Thomson valve, a Venturi device, a liquid expander, and a hydraulic turbine. The now lower pressure, partially liquefied sub-cooling stream 248 is sent to the surge tank 252, where the liquefied fraction 254 is removed from the process as an LNG stream 256 with a temperature corresponding to the boiling pressure. The residual steam fraction (flash steam) stream 258 can be used as fuel to power the compression unit.

FIG. 3 is a schematic diagram showing a liquefaction system 300 according to another aspect of the present disclosure. The liquefaction system 300 is similar to the liquefaction system 200, and for the sake of simplicity, components similarly drawn or numbered may not be mentioned further. The liquefaction system 300 includes a primary cooling loop 302 and a sub-cooling loop 304. The liquefaction system 300 also includes first and second heat exchanger zones 301, 310. In contrast to the liquefaction system 200, all of the first hot refrigerant 308 is sent to the second heat exchanger zone 310 and within one or more heat exchangers 310a with the compressed cooling refrigerant flow 312. Heat exchange is performed to form a second hot refrigerant 309.

The first hot refrigerant stream 308 is at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone, more preferably at least 5.6 ° C (10 ° F) colder, more preferably. It has a cold temperature of at least 8.3 ° C (15 ° F). The second warm refrigerant flow 309 is compressed in one or more compressors 318, 320 to a pressure greater than 10342 kPa (1,500 psia), more preferably to a pressure of approximately 20664 kPa (3,000 psia), thereby creating a compressed refrigerant flow 322. May be formed. The compressed refrigerant stream 322 is then cooled in contact with the ambient cooling medium (air or water) to produce a compressed and cooled refrigerant stream 312, which is sent to the second heat exchanger zone 310. The compressed and further cooled refrigerant flow 313 expands almost equientropically in the expander 326 to produce the expanded cooling refrigerant flow 305.

The supply gas flow 306 is sent through the first heat exchange region 301 including the main heat exchanger 332 and the sub-cooling heat exchanger 336. Since all of the first hot refrigerant 308 is sent to the second heat exchanger zone 310, the number of main heat exchangers in the first heat exchanger zone 301 can be reduced. Within the sub-cooling loop 304, the expanded sub-cooling refrigerant flow 338 (preferably containing nitrogen) is discharged from the expander 340 and drawn through the sub-cooling heat exchanger 336 and the main heat exchanger 332. The expanded sub-cooling refrigerant flow 338 is then sent to the compression unit 342, where it is recompressed to a higher pressure and warmed. After leaving the compression unit 342, the recompressed subcooling refrigerant flow 344 is cooled in the cooler 346. The cooler 346 may be of the same type as the cooler 324, but any type of cooler may be used. After cooling, the recompressed sub-cooling refrigerant flow passes through the main heat exchanger 232 through indirect heat exchange with some or all of the expanded cooling refrigerant flow 305 and the expanded sub-cooling refrigerant flow 338. Further cooled. After exiting the first heat exchange region 301, the recompressed and cooled subcooling refrigerant flow expands through the expander 340 to provide the expanded subcooling refrigerant flow 338. It is recirculated through the first heat exchange region as described herein. Thus, the supply gas stream 306 is cooled, liquefied and subcooled within the first heat exchanger zone 301 to produce a subcooled gas stream 348. The sub-cooling gas stream 348 then expands to a lower pressure in the inflator 350 to form a liquefied fraction and a residual vapor fraction. The expander 350 may be any decompression device, and examples thereof include, but are not limited to, a valve, a control valve, a Joule-Thomson valve, a Venturi device, a liquid expander, and a hydraulic turbine. The now lower pressure and partially liquefied sub-cooling stream 348 is sent to the surge tank 352, where the liquefied fraction 354 is removed from the process as an LNG stream 356 with a temperature corresponding to the boiling pressure. .. The residual steam fraction (flash steam) stream 358 can be used as fuel to power the compression unit.

FIG. 4 is a schematic diagram showing a liquefaction system 400 according to another aspect of the present disclosure. The liquefaction system 400 is similar to the liquefaction system 200, and for the sake of simplicity, components similarly drawn or numbered may not be mentioned further. The liquefaction system 400 includes a primary cooling loop 402 and a sub-cooling loop 404. The liquefaction system 400 also includes first and second heat exchanger zones 401, 410. In the liquefaction system 400, the sub-cooling loop 404 is an open cooling loop in which a portion 449 of the expanded sub-cooling gas flow 448 is recirculated and used as the sub-cooling refrigerant flow. Specifically, a portion of the expanded sub-cooling gas stream 449 is sent through the first heat exchanger zone 401 as previously mentioned and then compressed within the compressor 442 and within the cooler 446. It is cooled by and reinserted into the supply gas stream 406. This sub-cooling refrigerant flow may be a single flow or may include multiple flows of different pressures, as shown in the figure, for example, a portion of 50% or less of the expanded sub-cooling gas flow deviates. The pressure may be reduced to a range of about 207 to 2070 kPa (30 to 300 psia) through one or more pressure reducing valves, thereby producing one or more pressure reducing gas streams. The decompression gas stream can then be passed through the first heat exchanger zone as a sub-cooling refrigerant. Having multiple streams improves the efficiency of the sub-cooling process. Alternatively, the sub-cooling loop may be configured to be a closed cooling loop.

FIG. 5 is a schematic diagram showing a liquefaction system 500 according to another aspect of the present disclosure. The liquefaction system 500 is similar to the liquefaction system 200, and for the sake of simplicity, components similarly drawn or numbered may not be mentioned further. The liquefaction system 500 includes a primary cooling loop 502 and a sub-cooling loop 504. The liquefaction system 500 also includes first and second heat exchanger zones 501, 510. The flow of the liquefaction system 500 is cooled and compressed by compressing the supply gas flow 506 in the compressor 560 and then cooling the compressed supply gas 561 with ambient air or water using the cooler 562. Includes an additional step to generate the supplied gas flow 563. The compression of the feed gas can be used to improve the overall efficiency of the liquefaction process and increase the amount of LNG produced.

FIG. 6 is a schematic diagram showing a liquefaction system 600 according to another aspect of the present disclosure. The liquefaction system 600 is similar to the liquefaction system 300, and for the sake of simplicity, components similarly drawn or numbered may not be mentioned further. The liquefaction system 600 includes a primary cooling loop 602 and a sub-cooling loop 604. The liquefaction system 600 also includes first and second heat exchanger zones 601, 610. The liquefaction system 600 includes an additional step of cooling the supply gas stream 606 to a temperature below ambient temperature within the external cooling unit 665 to generate a cooling gas stream 667. The cooling gas stream 667 is then sent to the first heat exchanger zone 601 as described above. As shown in FIG. 6, the supply gas cooling step can be used to improve the overall efficiency of the liquefaction process and increase the amount of LNG produced.

FIG. 7 is a schematic diagram showing a liquefaction system 700 according to another aspect of the present disclosure. The liquefaction system 700 is similar to the liquefaction system 200, and for simplicity, components similarly drawn or numbered may not be mentioned further. The liquefaction system 700 includes a primary cooling loop 702 and a sub-cooling loop 704. The liquefaction system 700 also includes first and second heat exchanger zones 701 and 710. The liquefaction system 700 includes an additional step of cooling the compressed cooling refrigerant 712 into a primary cooling loop 702 using an external cooling unit 770 to a temperature below ambient temperature, thereby producing a compressed cooling refrigerant 772. The compressed cooling refrigerant 772 is then sent to the second heat exchanger zone 710 as described above. An external cooling unit can be used to further cool the compressed cooling refrigerant to improve the overall efficiency of the liquefaction process and increase the amount of LNG produced.

FIG. 8 is a schematic diagram showing a liquefaction system 800 according to another aspect of the present disclosure. The liquefaction system 800 is similar to the liquefaction system 300, and for simplicity, components similarly drawn or numbered may not be mentioned further. The liquefaction system 800 includes a primary cooling loop 802 and a sub-cooling loop 804. The liquefaction system 800 also includes first and second heat exchanger zones 801, 810. In the liquefaction system 800, the supply gas stream 806 is compressed in the compressor 860 to a pressure of at least 10342 kPa (1,500 psia) to form the compressed gas stream 861. Using the external cooling unit 862, the compressed gas stream 861 is cooled by indirect heat exchange with air or water at ambient temperature to form a compressed cooling gas stream 863. This compressed cooling gas stream 863 is less than 13790 kPa (2,000 psia) in at least one workpiece-forming inflator 874, but this gas stream expands to a pressure below the compressed pressure, thereby cooling gas. Form flow 876. The cooling gas flow 876 is then sent to the first heat exchanger zone 801 where the cooling gas flow is liquefied using the primary cooling refrigerant and the sub-cooling refrigerant as described above.

The sub-cooling loop 804 is preferably a closed cooling loop filled with nitrogen as a sub-cooling refrigerant stream. Within the primary cooling loop 802, the expanded cooling refrigerant flow 805 is sent to the first heat exchanger zone 801 to exchange heat with the cooling gas flow 876 to form the first warm refrigerant flow 808. The first hot refrigerant flow 808 is sent to the second heat exchanger zone 810 to exchange heat with the compressed cooling refrigerant flow 825 to further cool the compressed cooling refrigerant flow 825, thereby the second. Form a warm refrigerant stream 809 and a compressed and further cooled refrigerant stream 813. The first hot refrigerant flow 808 is at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone 801, more preferably at least 5.6 ° C (10 ° F) colder, even more preferably. Has a cold temperature of at least 8.3 ° C (15 ° F). Using one or more compressors 818, 820, the second warm refrigerant flow 809 is compressed to a pressure above 10342 kPa (1,500 psia), more preferably to a pressure of approximately 20664 kPa (3,000 psia). To form. The compressed refrigerant stream 822 is then cooled in contact with the ambient cooling medium (air or water) in the external cooling unit 824 to produce a compressed cooling refrigerant stream 825. After being sent through the second heat exchange region 810, the compressed and further cooled refrigerant stream expands almost equientropically within the expander 826 to produce the expanded cooling refrigerant 805. Within the first heat exchanger zone, the cooling gas stream 876 is liquefied and subcooled to produce a subcooling gas stream 848. This is further processed as described above.

FIG. 9 is a schematic diagram showing a liquefaction system 900 according to yet another aspect of the present disclosure. The liquefaction system 900 contains similar structures and components to the previously disclosed liquefaction system and may not further mention components similarly drawn or numbered for simplicity. The liquefaction system 900 includes a primary cooling loop 902 and a sub-cooling loop 904. The liquefaction system 900 also includes first and second heat exchanger zones 901 and 910. In the liquefaction system 900, the supply gas flow 906 is mixed with the refrigerant flow 907 to generate a second supply gas flow 906a. The second supply gas stream 906a is compressed using a compressor 960 to a pressure above 10342 kPa (1,500 psia), more preferably to a pressure of approximately 20664 kPa (3,000 psia), and the compressed second gas stream 961. To form. The compressed second gas stream 961 is then cooled in contact with the ambient cooling medium (air or water) using an external cooling unit 962 to produce a compressed and cooled second gas stream 963. .. This compressed and cooled second gas stream 963 is sent to the second heat exchanger zone 910, where it exchanges heat with the first hot refrigerant stream 908, where it is compressed and further cooled. A gas stream 913 and a second warm refrigerant stream 909 are generated.

The compressed and further cooled second gas stream 913 is less than 13790 kPa (2,000 psia) in at least one workpiece-forming inflator 926, but the second gas stream 906a does not exceed the compressed pressure. It expands to pressure, thereby forming an expanded and cooled second gas stream 980. The expanded and cooled second gas stream 980 is divided into a first expanded refrigerant stream 905 and a cooling supply gas stream 906b. The first expanded refrigerant flow 905 can be expanded almost equitropically using the expander 982 to form the second expanded refrigerant flow 905a. The cooling supply gas stream 906b is sent to the first heat exchanger zone 901, where the primary cooling refrigerant (ie, the second expanded refrigerant stream 905a) and the sub-cooling refrigerant (from the sub-cooling loop 904) are used. The cooling gas stream 906b is liquefied. The sub-cooling loop 904 may preferably be a closed cooling loop filled with nitrogen as the sub-cooling refrigerant. Within the primary cooling loop 902, the second expanded refrigerant flow 905a is sent to the first heat exchanger zone 901 where it exchanges heat with the cooling supply gas flow 906b to form the first warm refrigerant flow 908. The first warm refrigerant flow 908 is at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone 901, more preferably at least 5.6 ° C (10 ° F) colder, even more preferably. Can have a cold temperature of at least 8.3 ° C (15 ° F). The second warm refrigerant flow 909 is compressed in one or more compressors 918 and then cooled in an external cooling device 924 by an ambient cooling medium to generate a refrigerant flow 907. The cooling supply gas stream 906b is liquefied and subcooled in the first heat exchanger zone 901 to produce a subcooling gas stream 948. It is processed to form LNG as previously mentioned.

The aspects of the present disclosure shown in FIG. 9 demonstrate that the primary refrigerant stream may include a portion of the supply gas stream, which may be predominantly or almost entirely methane in a preferred embodiment. In fact, the refrigerant in all disclosure embodiments (ie, Figures 2-9) is at least 85% methane, or at least 90% methane, or at least 95% methane, or more than 95% methane. It can be advantageous to be configured. This is because methane may be readily available in various parts of the disclosure process, and the use of methane can eliminate the need to transport the refrigerant to remote LNG processing sites. As a non-limiting example, if the supply gas has a sufficiently large amount of methane and satisfies the above composition, the refrigerant in the primary cooling loop 202 of FIG. 2 can be taken in via the line 206a of the supply gas flow 206. Alternatively, some or all of the boil-off gas stream 259 from the LNG storage tank 257 may be used to supply the refrigerant for the primary cooling loop 202. Further, if the supply gas stream is low in nitrogen, some or all of the final flush gas stream 258 (which results in low nitrogen) may be used to supply the refrigerant for the primary cooling loop 202. .. Finally, any combination of line 206a, boil-off gas stream 259, and final flush gas stream 258 may be used to provide or sometimes replenish the refrigerant in the primary cooling loop 202.

Figure 10 shows a method of liquefying a methane-rich feed gas stream using a system with first and second heat exchanger zones, the following steps: 1002, feed gas stream less than 8274 kPa (1,200 psia). Prepare with pressure; prepare a compressed refrigerant stream with a pressure of 1004, 10342 kPa (1,500 psia) or higher; 1006, cool and compress this compressed refrigerant stream by indirect heat exchange with ambient temperature air or water. To generate a cooled and cooled refrigerant stream; 1008, this compressed and cooled refrigerant stream is sent to a second heat exchanger zone to further cool the compressed and cooled refrigerant stream below ambient temperature. To generate a compressed and further cooled refrigerant flow; 1010, this compressed and further cooled refrigerant flow is expanded in at least one work-forming inflator, thereby producing the expanded cooling refrigerant flow. To produce; 1012, this expanded cooling refrigerant flow is passed through the first heat exchanger zone to form a first warm refrigerant flow (this first warm refrigerant flow is the first heat exchanger zone). Has a temperature at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in); 1014, the supply gas is passed through the first heat exchanger zone and supplied by indirect heat exchange with the expanded cooling refrigerant flow. Cooling at least part of the stream, thereby forming a liquefied gas stream; 1016, sending at least part of the first warm refrigerant stream to the second heat exchanger zone, compressed by indirect heat exchange. In the flow diagram of Method 1000, which comprises cooling the cooled refrigerant flow, thereby forming a second warm refrigerant stream; and 1018, compressing the second warm refrigerant stream to generate a compressed refrigerant stream. be.

Figure 11 shows a method of liquefying a methane-rich feed gas stream, the following step: preparing the feed gas stream at a pressure of less than 1102, 8274 kPa (1,200 psia); 1104, this feed gas stream at least 10342 kPa (1104). Compressing to a pressure of 1,500 psia) to form a compressed gas stream; 1106, cooling this compressed gas stream by indirect heat exchange with ambient temperature air or water to form a cooled compressed gas stream. 1108, this cooled compressed gas stream is expanded in at least one workpiece-forming inflator to a pressure of less than 13790 kPa (2,000 psia) and below the compressed pressure, thereby forming a cooling gas stream. That; prepare a compressed refrigerant stream with a pressure of 1110, 10342 kPa (1,500 psia) or higher; 1112, this compressed refrigerant stream is cooled, compressed and cooled by indirect heat exchange with ambient temperature air or water. Forming a stream of refrigerant; 1114, this compressed and cooled stream of refrigerant is sent to a second heat exchanger zone to further cool the stream of compressed and cooled refrigerant below ambient temperature for compression. To generate a further cooled refrigerant flow; 1116, to inflate this compressed and further cooled refrigerant flow in at least one workpiece-generating inflator, thereby producing an expanded cooling refrigerant flow; 1118, this expanded cooling refrigerant flow is passed through the first heat exchanger zone to form a first warm refrigerant flow (so that the first warm refrigerant flow is the highest in the first heat exchanger zone. Has a temperature at least 2.8 ° C (5 ° F) cooler than the fluid temperature); 1120, indirect heat with the cooling refrigerant that has expanded at least part of the cooling gas flow through the first heat exchanger zone. Cooling by exchange, thereby forming a liquefied gas stream; 1122, sending the first hot refrigerant stream to the second heat exchanger zone to cool the compressed and cooled refrigerant stream by indirect heat exchange. , Thereby forming a second warm refrigerant stream; and 1124, a flow diagram of method 1100 comprising compressing the second warm refrigerant stream to generate a compressed refrigerant stream.

Figure 12 shows a method of liquefying a methane-rich feed gas stream, the following step: preparing the feed gas stream at a pressure of less than 1202, 8274 kPa (1,200 psia); 1204, almost the same pressure as this feed gas stream. Prepare the refrigerant flow in 1206, mix the supply gas flow with the refrigerant flow to form a second gas flow; 1208, compress this second gas flow to a pressure of at least 10342 kPa (1,500 psia). To form a compressed second gas stream; 1210, the compressed and cooled second gas stream is cooled by indirect heat exchange with ambient temperature air or water. Forming two gas streams; 1212, this compressed and cooled second gas stream is sent to the second heat exchanger zone to send the compressed and cooled second gas stream below ambient temperature. Further cooling to generate a second gas stream that is compressed and further cooled; 1214, this compressed and further cooled second gas stream is 13790 kPa in at least one work-making inflator. Inflating the second gas stream to a pressure less than (2,000 psia) and below the compressed pressure, thereby expanding and forming a cooled second gas stream; 1216, this expanded and cooled Dividing the second gas flow into a first expanding refrigerant flow and a cooling gas flow; 1218, expanding the first expanding refrigerant flow in at least one workpiece-generating inflator, thereby causing the second expanding refrigerant flow. To produce; 1220, this second expanding refrigerant flow is passed through the first heat exchanger zone to form a first warm refrigerant flow (as a result, the first warm refrigerant flow is the first heat. Has a temperature at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the exchanger zone); 1222, pass the cooling gas stream through the first heat exchanger zone and pass at least part of the cooling gas stream to the second Cooling by indirect heat exchange with the expanding refrigerant stream, thereby forming a liquefied gas stream; 1224, sending the first warm refrigerant stream to the second heat exchanger zone, compressed and cooled first In a method 1200 involving cooling the gas stream of 2 by indirect heat exchange to form a second warm refrigerant stream; and 1226, compressing this second warm refrigerant stream to generate a refrigerant stream. be.

The steps shown in FIGS. 10-12 are provided for illustration purposes only and may not require a specific step to implement the disclosed methodology. In addition, Figures 10-12 may not show all of the steps that can be performed. Only the claims, and the claims, define the disclosure system and methodology.
The embodiments described herein have several advantages over known techniques. For example, the techniques described can significantly reduce the size and cost of systems that process sour natural gas.
It should be understood that many changes, amendments, and alternatives may be made to the above disclosure without departing from the scope of this disclosure. Therefore, the above description does not mean limiting the scope of the present disclosure. More precisely, the scope of this disclosure should be determined only by the appended claims and their equivalents. It is also contemplated that the structures and features of this example can be modified, reorganized, replaced, deleted, duplicated, combined, or added to each other.
The present invention also includes the following matters.
(Appendix 1)
A method of liquefying a methane-rich supply gas stream using a system with first and second heat exchanger zones, described below:
(a) Prepare the supply gas stream at a pressure of less than 8274 kPa (1,200 psia);
(b) Prepare a compressed refrigerant flow with a pressure of 10342 kPa (1,500 psia) or higher;
(c) Cooling the compressed refrigerant stream by indirect heat exchange with ambient temperature air or water to produce a compressed and cooled refrigerant stream;
(d) The compressed and cooled refrigerant stream is sent to the second heat exchanger zone to further cool the compressed and cooled refrigerant stream below ambient temperature to be compressed and further cooled. To generate a flow of refrigerant;
(e) Expanding the compressed and further cooled refrigerant flow in at least one work-forming expander to generate an expanded cooling refrigerant flow;
(f) Passing the expanded cooling refrigerant flow through the first heat exchanger zone to form a first warm refrigerant flow (the first warm refrigerant flow is the first heat exchanger zone). Has a temperature at least 2.8 ° C (5 ° F) cooler than the highest fluid temperature in);
(g) The supply gas flow is passed through the first heat exchanger zone and at least a part of the supply gas flow is cooled by indirect heat exchange with the expanded cooling refrigerant flow, thereby causing the liquefied gas flow. To form;
(h) At least a portion of the first hot refrigerant stream is sent to the second heat exchanger zone to cool the compressed and cooled refrigerant stream by indirect heat exchange, thereby cooling the second. Forming a hot refrigerant flow; and
(i) Compressing the second warm refrigerant flow to generate the compressed refrigerant flow.
The method described above.
(Appendix 2)
The method of Appendix 1, wherein the first hot refrigerant stream has a temperature that is at least 5.6 ° C (10 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone.
(Appendix 3)
Note that a part of the first hot refrigerant flow remaining in the first heat exchanger zone further exchanges heat in the first heat exchanger zone to generate a third hot refrigerant flow. The method according to any one of 1 and 2.
(Appendix 4)
Further below:
Mixing the second warm refrigerant stream with the third warm refrigerant stream before compressing the second warm refrigerant stream.
The method according to any one of Appendix 1 to 3, including.
(Appendix 5)
Further below:
Further cooling the liquefied gas stream in the first heat exchanger zone using a sub-cooling cycle, thereby forming a sub-cooling gas stream.
The method according to any one of Appendix 1 to 4, including.
(Appendix 6)
Further below:
Expanding the sub-cooling gas flow in a hydraulic turbine to a pressure of 345 kPa (50 psia) or more and 3103 kPa (450 psia) or less to generate an expanded sub-cooling gas flow.
The method according to any one of Appendix 1 to 5, including.
(Appendix 7)
The method of Appendix 5, wherein the sub-cooling cycle comprises a closed-loop gas phase cooling cycle using nitrogen as the refrigerant.
(Appendix 8)
The sub-cooling cycle is as follows:
Take out the portion of the expanded sub-cooling gas flow that does not exceed 50% and reduce its pressure in the pressure reducing valve to a range of about 207 to 2070 kPa (30 to 300 pisa) to generate one or more decompression gas flows;
Passing the decompressed gas flow through the first heat exchanger zone as a sub-cooling refrigerant.
The method described in Appendix 6, including.
(Appendix 9)
The method according to Appendix 8, wherein the one or more decompressed gas streams include two or more decompressed gas streams having different pressures from each other.
(Appendix 10)
Further below:
Compressing the sub-cooling refrigerant flow exiting the first heat exchanger zone; and
The sub-cooling refrigerant flow is cooled by indirect heat exchange with air or water at an ambient temperature, and then the sub-cooling refrigerant is added to the gas flow.
The method described in Appendix 8, including.
(Appendix 11)
The method according to Appendix 6, wherein at least a part of the expanded sub-cooling gas flow is further expanded and then sent to a separation tank, liquid natural gas is taken out from the separation tank, and residual gas vapor is taken out as a flash gas flow.
(Appendix 12)
All of the first hot refrigerant flow is sent to the second heat exchanger zone to cool the compressed and cooled refrigerant flow by indirect heat exchange, thereby causing the second warm refrigerant flow. The method according to any one of Appendix 1 to 11, which is formed.
(Appendix 13)
Further below:
Before sending the supply gas flow to the first heat exchanger zone, the supply gas flow is compressed to a pressure of less than 11032 kPa (1,600 psia) and then it is exchanged for indirect heat with air or water at ambient temperature. To cool
The method according to any one of Appendix 1 to 12, including.
(Appendix 14)
Item 1 of Appendix 1 to 13, wherein the supply gas flow is cooled to a temperature lower than the ambient temperature by indirect heat exchange in the external cooling unit before the supply gas flow is sent to the first heat exchanger zone. The method described in.
(Appendix 15)
The compressed and cooled refrigerant stream is cooled to a temperature below ambient temperature by indirect heat exchange within the external cooling unit before the compressed and cooled refrigerant stream is sent to the second heat exchanger zone. The method according to any one of Appendix 1 to 14.
(Appendix 16)
A system for liquefying a methane-rich supply gas stream that has first and second heat exchanger zones and:
Supply gas flow with pressure less than 8274 kPa (1,200 psia);
Compressed refrigerant flow with a pressure of 10342 kPa (1,500 psia) or higher;
A cooler configured to cool the compressed refrigerant stream by indirect heat exchange with ambient temperature air or water to produce a compressed and cooled refrigerant stream;
The second, wherein the compressed and cooled refrigerant stream is sent to further cool the compressed and cooled refrigerant stream below ambient temperature, thereby producing a compressed and further cooled refrigerant stream. At least one heat exchanger in the heat exchanger zone;
At least one work-generating expander arranged to expand the compressed and further cooled refrigerant stream, thereby producing an expanded cooling refrigerant stream;
At least one heat exchanger in the first heat exchanger zone through which the expanded cooling refrigerant flow is passed to form a first warm refrigerant flow (the first warm refrigerant flow is said first. Has a temperature at least 2.8 ° C (5 ° F) cooler than the maximum fluid temperature in the heat exchanger zone);
(Here, the supply gas flow is passed through the first heat exchanger zone, and at least a part of the supply gas flow is cooled by indirect heat exchange with the expanded cooling refrigerant flow, thereby liquefying. Form a gas stream;
At least a portion of the first hot refrigerant stream is sent to the second heat exchanger zone to cool the compressed and cooled refrigerant stream by indirect heat exchange, thereby cooling the second temperature. Form a refrigerant flow); and
A compressor configured to compress the second warm refrigerant flow to generate the compressed refrigerant flow.
The system including.
(Appendix 17)
The system according to Appendix 16, wherein the first hot refrigerant stream is at least 5.6 ° C (10 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone.
(Appendix 18)
At least a part of the first hot refrigerant flow remaining in the first heat exchanger zone further heat exchanges in the first heat exchanger zone to generate a third warm refrigerant flow. , The system according to any one of Appendix 16 to 17.
(Appendix 19)
The system according to any one of Appendix 16-18, wherein the second warm refrigerant stream is mixed with the third warm refrigerant stream before compressing the second warm refrigerant stream.
(Appendix 20)
Further below:
A sub-cooling cycle configured to further cool the liquefied gas stream within the first heat exchanger zone, thereby forming a sub-cooling gas stream.
The system according to any one of Appendix 16 to 19, including.
(Appendix 21)
Further below:
An additional expander configured to generate an expanded sub-cooling gas stream by expanding the sub-cooling gas stream to a pressure of 345 kPa (50 psia) or higher and 3103 kPa (450 psia) or lower, including a hydraulic turbine.
The system according to any one of Appendix 16 to 20, including.
(Appendix 22)
20. The system of Appendix 20, wherein the sub-cooling cycle comprises a closed-loop gas phase cooling cycle using nitrogen as the refrigerant.
(Appendix 23)
Further below:
A pressure reducing valve configured to reduce the pressure in the portion not exceeding 50% of the expanded sub-cooling gas flow to a range of about 207 to 2070 kPa (30 to 300 psia), thereby producing one or more decompression gas flows. The one or more decompressed gas flows are passed through the first heat exchanger zone as the sub-cooling refrigerant).
The system described in Appendix 21, including.
(Appendix 24)
23. The system of Appendix 23, wherein the one or more decompressed gas streams comprises two or more decompressed gas streams having different pressures from each other.
(Appendix 25)
Further below:
A sub-cooling compressor configured to compress the sub-cooling refrigerant flow exiting the first heat exchanger zone; and
An external cooling unit configured to cool the sub-cooling refrigerant flow by indirect heat exchange with ambient temperature air or water.
The system described in Appendix 20, including.
(Appendix 26)
Further below:
An additional expander configured to further expand at least a portion of the expanded sub-cooling gas stream; and
Separation tank where the expanded sub-cooling gas stream is sent after passing through the additional expander
The system described in Appendix 21, including.
(Appendix 27)
Further below:
An additional compressor configured to compress the supply gas stream to a pressure of 11032 kPa (1,600 psia) or less before sending the supply gas stream to the first heat exchanger zone; and
An external cooling unit configured to cool the supply gas stream by indirect heat exchange with ambient temperature air or water.
The system according to any one of Appendix 16 to 26, including.
(Appendix 28)
Further below:
A second external cooling unit configured to cool the supply gas flow to a temperature below the ambient temperature by indirect heat exchange within the external cooling unit before sending the supply gas flow to the first heat exchanger zone.
The system according to any one of Appendix 16 to 27, including.
(Appendix 29)
Further below:
Before sending the compressed and cooled refrigerant stream to the second heat exchanger zone, the compressed and cooled refrigerant stream in which the compressed and cooled refrigerant stream is cooled to a temperature below the ambient temperature by indirect heat exchange. Configured third external cooling unit
The system according to any one of Appendix 16 to 28, including.
(Appendix 30)
The refrigerant in the primary cooling loop
The supply gas flow,
The flash gas flow and
Boil-off gas of the natural gas
Supplied from one or more of
The system described in Appendix 26.
(Appendix 31)
The system according to any one of Appendix 16-30, wherein at least one heat exchanger in the first heat exchanger zone comprises a brazed aluminum heat exchanger.
(Appendix 32)
The system according to any one of Supplementary note 16 to 31, wherein at least one heat exchanger in the second heat exchanger zone includes a printed circuit type heat exchanger.

Claims (18)

A method of liquefying a methane-rich supply gas stream (206) using a system (200) having first and second heat exchanger zones (201, 210), the following:
(A) Preparing the supply gas stream (206) at a pressure of less than 8274 kPa (1,200 psia);
(B) Prepare a compressed refrigerant flow (222) having a pressure of 10342 kPa (1,500 psia) or more;
(C) Cooling the compressed refrigerant stream by indirect heat exchange (224) with ambient temperature air or water to produce a compressed and cooled refrigerant stream (212);
(D) The compressed and cooled refrigerant stream is sent to the second heat exchanger zone (210) to further cool and compress the compressed and cooled refrigerant stream below ambient temperature. To generate a further cooled refrigerant flow (213);
(E) The compressed and further cooled refrigerant flow is expanded in at least one work-generating expander (226) to generate an expanded cooling refrigerant flow (205);
(F) The expanded cooling refrigerant flow is passed through the first main heat exchanger (234) in the first heat exchanger zone (201 ) to form the first warm refrigerant flow (208). It was to be the first temperature refrigerant stream to at least 2.8 ℃ (5 ° F) cooler temperature than the highest temperature of the fluid in said first heat exchanger zone;
(G) The supply gas flow (206) is passed through the first heat exchanger zone (201), and at least a part of the supply gas flow is exchanged by indirect heat exchange with the expanded cooling refrigerant flow (205). Cooling, thereby forming a liquefied gas stream;
(H) The first warm refrigerant flow drawn out at a position between the first main heat exchanger (234) and the second main heat exchanger (232) in the first heat exchange zone. Is sent to the second heat exchanger zone (210a) to cool the compressed and cooled refrigerant stream (212) by indirect heat exchange, thereby cooling the second warm refrigerant stream (209). ) To form;
(I) The remainder (208a) of the first hot refrigerant flow is passed through the second main heat exchanger (232) to exchange heat with the supply gas flow (206), thereby exchanging heat. Forming a third warm refrigerant stream (214);
(J) Combining the second warm refrigerant flow (209) with the third warm refrigerant flow to form a fourth warm refrigerant flow (216); and (k) combining the fourth warm refrigerant flow. The method comprising compressing to generate the compressed refrigerant stream (222). The method of claim 1, wherein the first warm refrigerant stream (208) has a temperature that is at least 5.6 ° C (10 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone. Further below:
The liquefied gas stream is further cooled in the first heat exchanger zone (201) using a sub-cooling cycle (204) with a sub-cooling refrigerant, thereby forming a sub-cooling gas stream (248). The method according to any one of claims 1 and 2, which comprises the above. Further below:
The third aspect of claim 3, wherein the sub-cooling gas flow is expanded in the hydraulic turbine (250) to a pressure of 345 kPa (50 psia) or more and 3103 kPa (450 psia) or less to generate an expanded sub-cooling gas flow. Method. The method of claim 3, wherein the sub-cooling cycle (204) comprises a closed-loop gas phase cooling cycle using nitrogen as the refrigerant. Further below:
Before sending the supply gas flow to the first heat exchanger zone, the supply gas flow is compressed to a pressure of 11032 kPa (1,600 psia) or less and then indirect heat exchange with air or water at ambient temperature. The method of claim 1, comprising cooling by. The first aspect of the present invention, wherein the supply gas flow is cooled to a temperature lower than the ambient temperature by indirect heat exchange in the external cooling unit (665) before the supply gas flow is sent to the first heat exchanger zone. Method. The compressed and cooled refrigerant flow is below ambient temperature by indirect heat exchange within the external cooling unit (770) prior to sending the compressed and cooled refrigerant flow to the second heat exchanger zone. The method of claim 1, wherein the method is cooled to a temperature. A system (200) for liquefying a methane-rich supply gas stream, having first and second heat exchanger zones (201, 210), and:
Supply gas flow (206) with a pressure of less than 8274 kPa (1,200 psia);
Compressed refrigerant flow (222) with a pressure of 10342 kPa (1,500 psia) or higher;
A cooler (224) configured to cool the compressed refrigerant stream by indirect heat exchange with ambient temperature air or water to produce a compressed and cooled refrigerant stream (212);
The compressed and cooled refrigerant stream is sent to further cool the compressed and cooled refrigerant stream below ambient temperature, thereby producing a compressed and further cooled refrigerant stream (213). At least one heat exchanger (210a) in the second heat exchanger zone;
At least one work-generating expander (226) arranged to expand the compressed and further cooled refrigerant stream, thereby producing an expanded cooling refrigerant stream (205);
A first main heat exchanger in said first heat exchanger zone (234) and a second main heat exchanger (23 2), said expanded cooled in the first heat exchanger zone first temperature refrigerant flow refrigerant stream is passed through the first main heat exchanger (208) is formed, said first temperature refrigerant flow, maximum fluid temperature in the first heat exchanger zone First main heat exchanger (234) and second main heat exchanger (232) having a cooler temperature of at least 2.8 ° C (5 ° F);
With
The supply gas flow is passed through the first heat exchanger zone, and at least a part of the supply gas flow is cooled by indirect heat exchange with the expanded cooling refrigerant flow, thereby forming a liquefied gas flow. death,
A part of the first hot refrigerant flow drawn between the first main heat exchanger (234) and the second main heat exchanger (232) is the second heat exchanger zone ( Directed to 210), the compressed and cooled refrigerant stream (212) is cooled by indirect heat exchange, thereby forming a second warm refrigerant stream (209).
The rest of the first warm refrigerant stream (208a) is passed through the second main heat exchanger (232) and exchanges heat with the supply gas stream (206), whereby a third. Forming a hot refrigerant flow (214),
The second warm refrigerant flow (209) and the third warm refrigerant flow (214) are combined to form a fourth warm refrigerant flow.
Compressors (218, 220) configured to compress the fourth warm refrigerant stream to generate the compressed refrigerant stream (222).
The system including. 9. The system of claim 9, wherein the first hot refrigerant stream has a temperature that is at least 5.6 ° C (10 ° F) cooler than the maximum fluid temperature in the first heat exchanger zone. Further below:
A sub-cooling cycle (204) configured to further cool the liquefied gas stream within the first heat exchanger zone, thereby forming a sub-cooling gas stream (248).
The system according to any one of claims 9 to 10. Further below:
An additional expander (250) configured to generate an expanded sub-cooling gas stream by expanding the sub-cooling gas stream to a pressure of 345 kPa (50 psia) or more and 3103 kPa (450 psia) or less.
The system according to any one of claims 9 to 11. 12. The system of claim 12, wherein the sub-cooling cycle comprises a closed-loop gas phase cooling cycle using nitrogen as the refrigerant. Further below:
An additional compressor (560) configured to compress the supply gas stream to a pressure of 11032 kPa (1,600 psia) or less before sending the supply gas stream to the first heat exchanger zone; and the supply. An external cooling unit (562) configured to cool the gas stream by indirect heat exchange with ambient temperature air or water.
9. The system of claim 9. Further below:
A second external cooling unit configured to cool the supply gas stream to a temperature below the ambient temperature by indirect heat exchange in it before sending the supply gas stream to the first heat exchanger zone. 665)
9. The system of claim 9. Further below:
Before sending the compressed and cooled refrigerant stream (712) to the second heat exchanger zone, the compressed and cooled refrigerant stream in which the compressed and cooled refrigerant stream is cooled to a temperature below ambient temperature by indirect heat exchange. Third external cooling unit ( 770 ) configured to
9. The system of claim 9. The system of claim 9, wherein at least one heat exchanger in the first heat exchanger zone comprises a brazed aluminum heat exchanger. The system of claim 9, wherein at least one heat exchanger in the second heat exchanger zone comprises a printed circuit heat exchanger.

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